Perform a double-blind randomized clinical trial to study the effectiveness of a commercially available vaginal contraceptive spermicide in preventing female genital tract infection by Neisseria gonorrhea and Chlamydia trachomatis. Eight hundred thirty women will be recruited for the trial from a sexually transmitted disease (STD) clinic in Birmingham, Alabama. They will be randomly assigned to receive either a spermicide preparation or a placebo. Subjects will be followed for six months; complete examinations will be performed every four weeks. The study infections will bedetected by cultural methods. Prior to the actual trial, in vitro testing of various commercial spermicides' inhibitionto N. gonorrhea and Chlamydia trachomatis will be performed and a suitable placebo chosen.